1. Field of the Invention
This document relates to an electrophoresis display, and more particularly, to an electrophoresis display which can reduce writing time of a memory.
2. Discussion of the Related Art
If a material having electric charge is placed in an electric field, the material peculiarly moves in accordance with electric charges, the size and shape of molecules and the like. Such a movement, i.e., a phenomenon in which materials are separated by the difference of movement, is named ‘Electrophoresis’. Recently, a display using electrophoresis has been developed and attention has been paid thereto as a medium with which a conventional paper medium or display could be replaced.
The display using electrophoresis has been disclosed in U.S. Pat. Nos. 7,012,600 and 7,119,772. The disclosed electrophoresis display compares current state images with next state images for each cell by use of a look-up table (LUT) 1, a plurality of memories 2 to 4, and a frame counter 5, as shown in FIG. 1, thereby determining the data V1 to Vn which are to be supplied to each cell for a plurality of frame periods.
The data V1 to Vn outputted from the look-up table 1 are digital data such as ‘00’, ‘01’, ‘10’ and ‘11’, and are changed to voltages of three states which are applied to a pixel electrode of each cell, that is, Ve+(+15V), Ve−(−15V), and Ve0(0V). ‘00’ and ‘11’ in the digital data is changed to Ve0(0V), ‘01’ is changed to Ve+(+15V), and ‘10’ is changed to Ve−(−15V).
FIG. 2 shows an example of a drive waveform which is supplied for a plurality of frame periods in accordance with a data written in the previous state and a data to be written in the current state. In FIG. 2, ‘W(11)’ represents a peak white gray level, ‘LG(10)’ represents a bright intermediate gray level, ‘DG(01)’ represents a dark intermediate gray level, and ‘B(00)’ represents a peak black gray level. And, the number written under the drive waveform is the number of frames.
A DC common voltage Vcom is supplied to a common electrode which is opposite to a pixel electrode. A positive data voltage Ve+ supplied to the pixel electrode is a voltage which is higher than the DC common voltage Vcom, and a negative data voltage Ve− is a voltage which is lower than the DC common voltage Vcom.
Such an electrophoresis display has the following problems.
As shown in FIG. 3, when display data is changed in a display panel every k (k is a natural number) frame periods, a control block 6 sets image data supplied from a system 5 during the current cycle as a current state image and stores it in a second memory 3, and sets the image data stored in the second memory 3 during the previous cycle as a previous state image and stores it in a first memory 2. The control block 6 compares the image data stored in the first and second memories 2 and 3, and generates digital data to be supplied to a data driving circuit by use of waveform information corresponding to the result of the comparison. And, the control block 6 sets image data supplied from the system 5 during the next cycle subsequent to the current cycle as the current state image to update the second memory 3, and sets the image data stored in the second memory 3 during the current cycle as the previous state image to update the first memory 2. The control block 6 compares the image data stored in the first and second memories 2 and 3, and generate digital data to be supplied to the data driving circuit by use of waveform information corresponding to the result of the comparison.
As seen from above, the electrophoresis display of the related art includes a first memory 2 for storing a previous state image only and a second memory 3 for storing a current state image only, and updates the first memory 2 and the second memory 3 every k frame periods so as to display image data on a display panel, thus increasing memory writing time and making driving complicated.